Hardshell venous reservoirs are used in extracorporeal bypass circuits during cardiac surgery to store the extra volume of blood produced in the patient's circulatory system by the dilution of the patient's blood in preparation for open heart surgery. The reservoir also serves as a buffer to absorb variations between the volume of blood exiting the patient through a venous tap and cardiotomy suction, and the volume of blood drawn by the pump of the heart-lung machine for oxygenation and return to the patient.
Conventionally, venous blood is introduced into the reservoir through a venous inlet connector which is fitted into the cover of the top entry reservoir, and which can be rotated about an axis perpendicular to the plane of the cover. Blood from the venous inlet connector is discharged into a venous flow tube which fits over the bottom end of the connector and conveys the blood to an appropriate venous defoamer chamber in the reservoir.
In order to minimize foaming and risk of contamination of the venous blood, it is essential that air be prevented from entering the blood stream at the interface of the flow tube and the connector. Prior art constructions have addressed that problem by providing one or more 0-ring seals between the connector and the flow tube. The prior art construction was, however, not completely satisfactory because, firstly, biocompatible silicone 0-rings are not inexpensive; because, secondly, their relatively high friction coefficient makes it harder than necessary to rotate the connectors; and because, thirdly, the patient's blood should be exposed to as few different materials as possible during surgery.
A need consequently existed in the prior art for an inexpensive, airtight rotatable joint between the telescoping connector and flow tube.